Swiss scientists have shown that an antibody called aducanumab could clear away beta-amyloid plaques in the brain, which are seen as hallmarks of the devastating disease.
Tackling these deposits has been seen as key to the hunt for treatment as extensive build-ups have been found in the brains of dead patients.
The last Alzheimer’s drug licensed in the UK came more than a decade ago.
Existing treatments can reduce symptoms rather than the progression of the disease, which affects 90,000 Scots.
Dr David Reynolds, chief scientific officer at Alzheimer’s Research UK, said: “In continued efforts to develop the first disease-modifying treatment for Alzheimer’s disease, these results provide tantalising evidence that a new class of drug to treat the disease may be on the horizon.
“The findings suggest that aducanumab may slow memory and thinking decline in people with early Alzheimer’s and although the analysis is only exploratory in this early trial, it paints a positive picture for ongoing trials with the drug.”
Experts gave 165 patients monthly infusions of aducanumab or a placebo for one year, resulting in significant reductions of beta-amyloid among those taking the drug.
Higher doses of the drug were associated with a reduction in cognitive decline among the mice, which has never been proven before.
Study author Roger M Nitsch, from Zurich University, said: “The results of this clinical study make us optimistic that we can potentially make a great step forward in treating Alzheimer’s disease.
“The effect of the antibody is very impressive. And the outcome is dependent on the dosage and length of treatment.”
Some patients suffered side effects such as headaches, according to the study published in Nature journal.
Leading neuroscientist Professor Richard Morris said he was impressed with the findings, which managed to overcome a number of hurdles. Prof Morris, from Edinburgh University, said: “We cannot yet say we have a cure for Alzheimer’s, as this is only a first step.
“However, despite being only 165 early stage patients, these encouraging results will likely help the company enormously to scale up to a full double-blind clinical trial of aducanumab.
“The conclusion that this study supports further development of aducanumab is fully justified and the importance of this first step cannot be understated. Let’s keep our fingers crossed for success in the next steps.”
Recruitment is now underway for trials in humans.